Post Fire in Southern California May Foreshadow a Hazardous Summer

A wildfire that quickly consumed more than 14,000 acres of grasslands and brush in a mountainous area northwest of Los Angeles over the weekend signaled the start of what experts warn could be a dangerous, prolonged fire season in the West.

“This is a taste of what’s to come,” said Daniel Swain, a climate scientist with the University of California, Los Angeles.

The blaze, named the Post fire, started on Saturday afternoon near Interstate 5 about 45 miles outside of Los Angeles, the authorities said. It forced the evacuation of about 1,200 people from the Hungry Valley campground, a popular state recreation area for off-road vehicles. Officials also closed nearby Pyramid Lake, a destination for weekend boaters.

As of Sunday afternoon, the fire was about 2 percent contained and ranked as the state’s largest wildfire so far this year, according to CalFire, California’s firefighting agency.

The Post fire burned about 10,000 acres within 12 hours after it ignited — a rapid spread fueled by hot, dry and windy conditions, said Kenichi Haskett, a spokesman for the Los Angeles County Fire Department. Winds gusting up to 50 miles per hour over ridge tops made firefighting efforts especially difficult. When firefighters dump water from planes, for example, “it just sprays everywhere,” Mr. Haskett said.

While strong winds were expected to continue through Sunday and into Monday, Mr. Haskett said that fire officials hoped to be able to make significant progress containing the blaze in coming days.

“Our goal is hopefully to be done within the week,” he said.

Two buildings — a campground kiosk and another recreational building — were damaged, Mr. Haskett said, but no homes had been burned so far.

Still, he said, officials were encouraging residents of the area surrounding Castaic Lake, another popular weekend destination, to prepare to leave, if winds continued to push the fire farther south.

On Sunday afternoon, another fast-moving brush fire, the Max fire, ignited about 50 miles to the east of the Post fire and burned through several hundred acres near homes in Lancaster, a city of about 170,000. Some residents were told to evacuate, though by Sunday evening the fire was fully contained, according to a social media post by the authorities in Palmdale, a city north of Los Angeles.

The Post fire alone seems unlikely to shatter records or cause widespread damage, said Dr. Swain. But the speed of its spread and the fact that it is still only mid-June illustrate why — even after two rainy winters — Californians should be on high alert as the summer unfolds, he added.

Climate change is driving wider swings between precipitation extremes. In California, whiplash between drought and deluge has been particularly intense in the last few years.

“There’s this cycle between wetter and drier conditions,” Dr. Swain said. “We’re used to that.”

Global warming trends, however, are exacerbating the effects of these swings, he said.

A record-breaking rainy season at the end of 2022 and into 2023 followed years of catastrophic drought. There was so much rain that deep into summer and autumn, when fire risk is typically higher, that vegetation that otherwise might be prone to burn was still green and damp.

Last winter in California was also rainy, which spurred the growth of even more vegetation.

But Dr. Swain said that late spring has been hot in the West — temperatures in Las Vegas broke records this month — and the sweltering air is expected to continue.

That heat sucks moisture out of the grasses and brush that have grown over the last two years, turning them into a thick carpet of tinder. The hotter and drier it is, the more quickly vegetation becomes fuel for fires.

“Even though dryness levels are not record-breaking at this point, what is anomalous is just how much fuel there is,” Dr. Swain said.

He said that grasslands tend to burn first, because grasses dry out the most quickly. But if hot, dry conditions persist and combine with fearsome autumn winds, like Southern California’s notorious Santa Ana winds, residents could see an active fire season that goes well into the fall.

Of course, residents of the West are still subject to some amount of chance: Lightning strikes and human accidents helped propel the 2020 wildfire season in California from bad to catastrophic.

State and federal officials have stepped up efforts to prevent wildfires, particularly with the use of prescribed burning, a practice of purposely starting fires — when conditions make them easy to contain — to reduce the amount of fuel on the ground.

But Dr. Swain emphasized that, regardless of any prevention efforts, climate change is making everything more unpredictable — and dangerous.

“The more adverse the conditions, the more likely it is you get unlucky,” he said.

Yan Zhuang contributed reporting.

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